Newton's Prism: Enlightenment Optics

The Enlightenment's scientific revolution ran on experiments you could see with your own eyes, and none is more famous than Isaac Newton's prism work of the 1660s–1700s. This simulation traces real rays of seven visible wavelengths through a glass prism using Snell's law at every face, showing exactly why white light fans out into a spectrum and why red always bends least. Adjust the incidence angle, the prism's own apex angle and the entry aperture to reproduce Newton's original finding, then switch on the converging lens to watch the spectrum recombine back into a single point of white light — his experimentum crucis in reverse.